Control apparatus for jet engines



Feb. 9, 1954 L. LEE u CONTROL APPARATUS` FOR JET ENGINES 4 sheets-sheet 1 ATTORNEY L. LEE ll CONTROL APPARATUS FOR JET ENGINES Feb. 9, 1954 Filed Dec. 5, 1948 l 4 Sheets-Shee't 2 4 Sheets-Sheet 3 JNVENTOR. [@yia/z Leal.

47m/vir L. LEE Il CONTROLAPPARATUS FOR JET ENGINES Feb. 9, 1954 Filed Dec. s, 1948 Feb. 9, 1954 l.. LEE u 2,568,414

CONTROL APPARATUS RoR JET ENGINES v Filed Dec. s, 194s 4 sheets-sheet 4 fn l) AN NN n S R f. n lul n b u Q t 2 2 R R f 7.90( @masa/J 0g A INVENTOR. @/yo/zeel.

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Patented Feb. 9, 1954 C QNTRQL. APPARATUS FOR JET ENGINES Leighton Lee IIL, Rocky Hill, Sonn.,` assigner to, Nilesrement-Pond Common, West Hartford, Conn., ai corporation of New-Jersey Application December 3, 1948;, Serial; No. 63,3%r 2Q Claims. (C1. (ie-139.248,),-

This invention relatesA to fuel and speed control apparatus for internal combustion engines, and more particularly has reference to intel-nal combustion engines suitable for propeller-propulsion, jet-propulsion, or propeller-and-jet propulsion of aircraft. Such engines usually include anY air inlet,A an air compressor, one or more combustion chambers, a gas turbine, and a tail pipe for discharging combustiongases to the atmosphere. Associated with the engine is a fuel system including a fuel pump for delivering iuel to the combustion chambers. This invention concerns apparatus to control the engine speed and power by controlling the fuelpomp delivery as a function of manual control and severall variables including engine speed, engine temperature, other engine operating conditions, as disclosedv in my copending application for Control Apparatus for Turbojet Engines," Serial No. 746,975, iled May 9, 1947;' and this invention constitutes an improvement on the invention therein disclosed. This application is aocordingly a continuation in part of my earlier application cited.

Objects of my invention are:

(l) To provide an improved fuel and speed control apparatus of the type disclosed in my parent application cited, wherein the droop of the speed control system is greatly reduced and the control may be made substantially isochronous.

(2) To provide an improved fuel and speed control apparatus of the type disclosed in my parent application cited, wherein better operating results are obtained with a greatly simplied .speed control mechanism.

(3) To provide improved fuel and speed control apparatus for an internal combustion engine employing the same principles and means disclosed in my parent application cited, except as to the speed control system .which herein makes the speed governor cut-in vary the control oil pressure by varying the pressure in` the compressor discharge bellows,` and thereby substantially reduces the droop of the speed control system.

(4) To provide in such apparatus improved mechanism for operating the barometric control system by the compressor discharge pressure.

Other objects and advantages of my invention will become apparent from a consideration of the appended speciiication, claims, and drawings, in which:

Figure 1 shows, somewhat diagrammatically, an engine suitablel for propellerAand-.jet propulsion. of aircraft, together withA its associated fuel pump and an engine con-trol lever, there being also shown principal connections between the engine and a diagrammatic illustration of the fuel: and speed` control apparatus of Fig. 2;

Figure 2 shows, also somewhat diagrammatically, fuel and speed control apparatus embodying the principles! of my invention;

Figurey 3 shows a modiication of certain elements of the construction shown in Figure 2, iaccording to another embodiment of my invenlon;

Figure 4 shows, diagrammatically, certain speed governor characteristics off my improved control apparatus.

In the drawings and specification, the same reference numerals as appear in my parent application cited, are used to denote those elements of; myinvention herein which are identical with the invention disclosed in said parent application.

Figure 1 Referring to the drawing, Fig., 1,y there are sho-wn the principal elements of the engine above referred to, a supporting casing It, an air inlot I2., a multi-stage oompressor i4, a oomnressl'or rotor shaft lo, one oooh of a number of oombostion Chambers. L3.. one of o. oorrespondne number of fuel discharge nozzles 20 conn.oo-todk to a generally circular manifold 22 by means of a conduit Z4', a multi-stage, turbine 26, a turbine rotor shaft 23 connected to the compressor rotor shaft I6, a tail pipe 38 for discharging combustion gases. from turbine. iii, a center booting 32 and end bearings 3,4` and 36. supported; by' easing lo. a proponer shaft n to which is fixed o oropelier- 40, and gear train 4.2. connecting shafts it and 3.o for rotating; propeller 4o. at a spoed proportional to engine, sneed and for operating the fuel mimo and other accessories Construcnon of a iet engine used solely for iet propolsion is similar to. that of the engine of Figure 1 except for omission of: the propeller and propeller shaft. and corresponding modification of the soar train. Since. in a iet. engine, the power oieveloped by the, turbine is used only for oper-atine the` compressor and: accessories, sin f1 stage rather than multi-stage turbine eonstruotion is generally employed.V y

A- fuel pump 44 has associated therewith delivery voryn'e means diaerammaallr shown an 4s. Pump at is connected to a pe p niet conduit 48 and to a pump discharge co lit M53. Fuel ows from the indicated sourcel of; supply through 'inlet conduit .4;8, pump 4 4, and pump discharge conduit 56 to manifold 22 in the engine. Pump 44 is operated by a drive shaft 45 connected to gear train 42 in the engine, or any other suitable source of power. The delivery varying means is responsive to a variable control oil pressure (pc) in a conduit 56 which is regulated by the control apparatus or" Fig. 2.

In each of the discharge nozzles there is a series of iixed slots, one of which is indicated at 2|, through which fuel enters the nozzles from conduits 24. The fuel flow from the nozzles is directly proportional to the effective area of slots 2| and is a square root function of the drop across the slots between the pressure in conduits 24, which is substantially equal to the pressure (pF) in conduit 50, and the pressure in the combustion chamber. It follows, therefore, that the fuel pump delivery is a function of the pressure (10F) in conduit 50 which is controlled by the delivery varying means 46.

When it is desired to limit the range of fuel pressure so that its valne at maximum fuel flow is less than that corresponding to the square root function of the drop across slots 2|, the nozzles may be provided with auxiliary slots supplied by Vanother manifold connected to conduit through a pressure-responsive now-divider which opens at a predetermined value of the pressure (pF). In this manner the pressure (pF) may be maintained sufficiently high to produce satisfactory nozzle discharge without requiring the pump to operate under unfavorable pressure conditions at maximum flow.

The control apparatus of Fig. 2, diagrammatically shown in Fig. l, is connected to a source of compressor discharge pressure (11D) in the engine by a conduit 52 and, as subsequently explained, the control apparatus is responsive to the pressure (pD), which is an indication of air flow through the engine. The value of the pressure (pD) increases as the engine speed increases, as flight speed increases, and the altitude of flight or entering air temperature decreases, and is also a function of the compressor characteristics.

A main drive shaft 58 in the control apparatus is driven by the engine at a speed proportional to engine speed and a main control shaft 60 is rotatable in response to movement of a shaft 62 to which is fixed an engine control lever 64. Control lever 64 is manually operable in reference to a scale 68 on a fixed quadrant 66, scale 68 being calibrated in terms of R. P. M. engine speed.

Figure 2 Referring to Fig. 2, there is shown, somewhat diagrammatically, an embodiment of my invention all principal elements of which, except a thermal control 10, are enclosed in a casing 12 having external connections with conduit 52 for supplying air to the apparatus at the compressor discharge pressure (pD), and with conduit 56 for transmission of the variable control oil pressure (pc) from the apparatus to the fuel pump delivery varying means 46 shown in Fig. l. Casing 12 as shown in the drawing is of continuous cross-section but for purposes of manufacture and assembly may be made in an equivalent form comprising two or more separable elements.

The control apparatus of Fig. 2 is a self-contained hydraulic system employing the interior of casing 12 as a reservoir 14 which is maintained approximately full of suitable hydraulic fluid at the pressure (p) in order to permit the working elements to operate in an oil bath and which is vented at a threaded port 16 to the atmosphere or other desired pressure source. If desired,

reservoir 14 may be made a part of the oil system of the engine. In this case, a pair of plugs 18 and otherwise serving as drain plugs are removed from casing 12 and the respective casing openings are then connected by suitable inlet and outlet conduits to the engine oil system. The main drive shaft 58 operates an hydraulic pump 82 which pumps fluid from reservoir 14 through an inlet port 84 and an outlet 86 into a charnber 88. The pressure (p1) in chamber 88 is maintained at a substantially constant value, approximately 240 p. s. i. in the embodiment shown, by a relief valve 90, which allows fluid to flow from chamber 88 past valve 90, through a chamber 94 and an aperture to reservoir 14 in opposition to a substantially constant force produced by a valve spring 98. Fluid from chamber 86 enters two main fluid conduits |04 and |06 downstream from a filter |00, and is conveyed at pressure (p1) to elements of the apparatus hereinafter specified.

The control apparatus comprises four mechanically and hydraulically cooperative component systems, as briefly outlined in the immediately following numbered paragraphs, for regulating the variable control oil pressure (pc). namely:

(l) A manual control system principally including a main servo valve |08, a main servo valve sleeve |09, a main power piston |10, a main floating lever H2, a push rod |14, and a cam ||6 fixed to the main control shaft 60, for rendering pressure (pc) variable by movement of the engine control lever 64, Fig. l. Also included in the manual control system, as set forth herein, is a lever mechanism |32 comprising a pair of levers |94 and |98, a circular bearing 208 between said levers, a spring 204, and a rod |92 for loading piston ||0 with a force due to spring 204. Fluid flows discontinuously to the manual control system through a conduit H8 connected to main fluid conduit |06 and is drained from the manual control system through an outlet passage |20 opening into reservoir 14 at the upper end of valve sleeve |09. The variable control oil pressure (pc) is transmitted from the manual control system through a conduit |22 which is connected to conduit 56.

(2) A barometric control system principally including a barometric servo valve |24, a barometric servo valve sleeve |25, a barometric power piston |26, a barometric floating lever |28, a xed elongated barometric cam |30, a positioning bar 286 for varying the position of bearing 208, and a pair of bellows |34 and E36, the former connected to conduit 52 and the latter evacuated to zero pressure p0 and sealed. The pressure (pc) is made a function of the compressor absolute discharge pressure (pn or pM) by transmission of movement of piston |26 through cam |30, positioning bar 286, and lever mechanism |32 to the main power piston i0 in the manual control system. Fluid ows discontinuously to the barometric control system through the main fluid conduit |06 and is drained from the barometric control system through one or the other of two outlet passages 98 and |46 in sleeve |25, which passages open into reservoir 14.

(3) A speed control system principally including a governor valve mechanism generally indicated at E42, a governor lever |44, which is secured in an adjustable position by a spring |45 and a screw |41 locked by a lock nut |49. In this system, the pressure (pc) is made a function of the engine speed by modifying the compressor movement `of an loven-.speed yservo valve |56.

Compressed air `under a pressure (pM), which is y.the compressor absolute discharge .pressure (10D) anodined byfarestriction 15.3..;-ows :through acon- .duiti55 to the `governor valve mechanism |42 and is discharged to atmosphere 'from .that valve .mechanism through .a conduit 5.1 .connected to .-.a governor valve. sleeve L56 therein.

i114) A .thermal control system including the thermal control 19 and `a thermal piston |55 for overriding the manual control system -as a func- -tion of the engine temperature. Normally, there is .no ow of Iflu-id through fthe thermal vcontrol system, but when the predetermined :limiting or .maximum `allowable temperatureis exceeded duid ows ff-rom main :fluid iconduit .|;96., successively through a conduit 5.'| past piston |55., and .through a Wconduit |69, thermal control 19, and a conduit |62 `13o-reservoir 14.

Manual control system A wall |64 is provided in -reservoir 14 vand is suitably bored or otherwise machined for housing and operating therein some elements of each ofthe four component control systems previously defined.

In the manual control system, a gear |66 is A provided at the lower end of main servo valve sleeve |99 -for rotation lof the sleevein wall |6fi, sleeve |99 having its upper endextending somewhat beyond the upper side `of the wall. Gear .|66 and sleeve |99 are rotated by another gear |69 fixed to a shaft |19 which in turn is driven from the main drive shaft 58 through a suitable connection (not shown). Similarly, a gear |14 is provided at the upper :end of piston ||9 which is both slida'bly and rotatably operable in wall |64 and is installed with gear |14 above the wall. Gear .|14 is rotated by another gear |76 iixed to the upper end of shaft |19. Any other means oi suitably rotating `sleeve |99 and piston ||9 may A be employed, the purpose of such rotation being to .avoid sticking of the main vservo valve |98 in sleeve |99 and to prevent -sticking of the piston lin wall |641.

Valve sleeve |99 is provided with a pair of parallel circumferential grooves .|18 and |199 and one or more ,corresponding yports |82. and |84 drilled radially at the horizontal .centers `of the grooves. The upper end of 4conduit ||8 opens 'x opposite groove |18 and ports |82 are therefore continuously `supplied with fluid at pressure (p1). Groove |89 is similarly connected to the upper end of a passage |88 which is connected to condu-it |22.

Valve |98 is undercut to form an annular .chamber v| 66 and has a neutralposition as shown lin Fig, 2 in which the lower edge of the undercut is alined with the upper edge of port |82, and the upper edge of the .undercut is :alined with the lower edge of outlet passage |29. Ports |84 communicate with chamber |86 regardless of the position of valve |98 inits normal range of operation. When valve |98 is displaced downwardso -that port |62 opens into 'chamber |86., .a path for .iiow is provided which successively includes conduit I8, groove 18, ports 82, vchamber 18S-,ports |84, groove |89, passage i 88., :and conduit |22, at the upper end of which there is an expansible chamber |99 included between .the lower end of piston H9 and Wall |64. Thefvalue :of the variable -control oil pressure (10e) 'in :conduit 56 and chamber |99 is thus increased Aupon idownward movement 'of valve -Hi8 from .itsneutral position.

tem, the pressure (pe) Similarly, when valve |98 `is displaced upward so .that chamber |86 opens .into outlet .passage 29, a path for flow is provided from conduit 56 A:and chamber |99, through passage I 63, groove L89, ports |94, vchamber |66, `and outlet passage |29 to reservoir '14, the pressure (pc) being .thereby decreased.

The left-.hand end of .main iioating lever .'|2|.2 yhas a pin-and-slot connection `|3 with rod |92 which has a yself-alining connection Vat its lower 'end with the .bored interior of piston |.|9 .so that .vertical movement of the piston .produces upward .movement of rod |92 and simultaneously allows angular displacement of the rod with respect .to the piston without causing the latter to bind in wail |66. The upper end of rod .|92 is hinged to the left-hand end of lever |94 in mechanism |32, lever lei having its .right-hand end hinged to afixed support |96. Above lever 94, .mec-hanisrn .|32 includes the lever |98 which has its left-hand end hinged at a pin 299 iixed ina support 2.92 above and approximately on the centerline of vpiston H9. The right-hand end of lever :|96 is connected to .tension spring 294 whichhas its lower end anchored in a fixed support 2.9.6. A measure of the downward force of spring .2.04 is transmitted from lever |98 to lever |94 through the circular bearing 299 the position of which is regarded as fixed in the present. discussion. Piston H9 is subjected -to van upward force Vproportional to the diherential (pc-p) between the respective pressures in chamber |99 and reservoir 7i and to a measure of the downward force of spring 2&9 which is transmitted to the piston through lever mechanism |32 and rod |92. The rate of spring 294is high, so that the value ofthe differential (pe-p) and hence the variable control oil pressure (pc) may vary throughout a'wide range of vaines corresponding to a relatively narrow range of movement of the piston which is .positioned by the resultant of the forces acting thereon.

The right-hand end of :main Afloating lever |2 engages an arm 366 pinned to a rod ||4 which contacts the upper face of a cam H6 fixed to main control shaft 69, hence the lever I 2 is positioned by: (l) push rod 4 and arm 366 which engages an adjusting screw 2|4 threaded .into Llever ||2 and locked in place by means of a nut `2|6; y(2) rod 92 which serves as a pivotal support forthe left-hand end of lever 2; and .(3) alight spring 2| 8 compressed between a xed support 229 land a retainer v222 sup-ported by the upper end of valve |93, which causes the lever V|.| 2 to follow movement of push rod 'l i4 as the latter 'isactuated by cam 6. It is to be noted from the above that, except for the substantially negligible vforce due to spring 2|6, the main servo valve |98 does -no-t directly affect the position of lever l l2 but instead is positioned `by that lever, there -being equal and opposite forces proportional to pressure (p) on the ends of valve |98. `When considering the manual control lsystem only, the position of bearing 293 and hence the downward force of rod |92 corresponding to any given position of piston H9 is regarded as xed. in the .neutral position of servo valve |96, as shown, the manual control system is in a state of equilibrium; i. e., there is no vflow of fluid in the sysis` such as to maintain piston .l 9 in a position corresponding to the position of cam ||6 and the neutral position of 4valve |98, and the pump delivery corresponds with .the value of pressure (pe) trapped inthe system lby :closure .of Lthe servo valve.

Upon clockwise movement of control lever 64, Fig. 1, and consequent clockwise movement of main control shaft 60 and cam H6, lever ||2 moves clockwise about connection |3 and servo valve |03 is depressed from its neutral position. Consequently, as previously explained, the value of pressure (pc) and hence the fuel ow to the engine increase. Pressure (pc) continues to increase until piston ||0 responds by raising lever i ||2 and valve 108 a sulicient amount to restore the valve to its neutral position, following which no further change occurs as long as the position of shaft 60 remains undisturbed. Similarly, upon counterolockwise movement of control lever 64, Fig. 1, and corresponding counterclockwise movement of shaft 66 and cam H6, lever ||2 moves counterclockwise about its connection with rod |62 and the servo valve is elevated above its neutral position. In this case, as previously explained, the value of pressure (pc) and hence the fuel flow decrease, continuing to do so until piston H0 responds by lowering rod |92 and lever ||2 to a new position at which servo valve |08 is `again restored to its neutral position. When servo valve |08 is in its neutral position, the value of pressure (pc) and hence the fuel flow is determined by the position of control shaft 66 for a given iixed position of bearing 208 in lever mechanism |32.

As stated earlier, the engine speed corresponding to any given value of fuel flow varies as a function of entering air density, flight speed, and other factors over which the manual control system has no control and to which it is unresponsive. It follows, therefore, that the manual control system provides a means of regulating the variable control oil pressure (pc) from minimum to maximum values vcorresponding to a predetermined range of clockwise movement of the engine control lever 64, Fig. l, and depending upon the downward force transmitted by rod |92 to piston ||0. 1

Speed control system Governor valve mechanism |42 includes a yball speed responsive device 224 operated by the main drive shaft 58 for varying the vertical position of governor valve sleeve |56 as a function of engine speed. The valve sleeve operates in a suitably bored projection 225 of `casing 12. The inner race of a ball bearing assembly 226 is fastened to the upper end of sleeve |56 and the outer race of bearing assembly 226 van upper governor spring retainer 236 which is Iforced upward by spring 234 against the left- Vhand end of setting lever 48. Bearing assembly 226 permits sleeve |56 to rotate while retainer 228 remains stationary and hence prevents torsional stress in spring 234.

Push rod assembly |46 is actuated by cam |50 in response to rotation of shaft 60 by the engine Vcontrol lever 64 (Fig. 1), for varying the position of setting lever |48 and the upper governor spring retainer 236, and hence for varying the load of spring 234 on valve sleeve 56 in opposition to the upward force of the speed responsive device 224. Assembly |46 includes the follower push rod 232 having its lower end slidably operable in a hollow sleeve formed on the upper end of a push rod 238 engaging cam |50. During a predetermined range of movement of control lever 64 in .which the enginespeed is manually variable, a

spring 240 maintains the overalllength of the assembly |46 at a value determined by engagement of a pin 242 in push rod 238 with the lower end of a slot 244 in follower push rod 232. When, however, setting leverl |48 engages an adjusting screw 246 so that further upward movement of rod 232 is prevented, upward movement of push rod 238 is permitted by compression of spring 240, the length of slot 244 and the distance between the lower end of rod 232 and the corresponding portion of rod 238 being sufficient to prevent jamming of the pushrod assembly.

In the particular embodiment shown, the downward force of governor spring 234 varies substantially directly with the spring deiiection, while the upward force due to speed responsive device 224 is proportional to the square of the engine speed. When these forces are in equilibrium, there is no vertical movement of sleeve |56. The position of the sleeve corresponding to a condition of equilibrium may vary over a predetermined range in which a port 248 in sleeve |56 opens into an annular recess 250 in projection 225. Cam |50 is generated so that as oontrol lever 64 is advanced clockwise throughout a predetermined range in reference to the uniformly calibrated R. P. M. scale-68 (Fig. 1), the dellection of spring 234 is varied at a non-uniform rate so that the speed required to produce a state of equilibruim increases according to the scale value corresponding to the position of the lever.

Recess 256 adjacent sleeve |56 is connected by conduit 55 to the interior of bellows |34 and the pressure (2o-M) in bellows |34 is controlled by governor valve sleeve |56 which cooperates with a governor valve 256. Valve 256 has a pin-andslot connection with governor lever |44 and is slidably operable inside sleeve |56 only in response to the adjustment of lever |44 by adjustment screw |41. The governor valve 256 is undercut to provide an annular chamber 26| which is connected through a port 262 and annular groove l263 in sleeve |56 with the inner end of discharge conduit 51 in all positions of sleeve |56 within its working range. The land at the lower end of valve 256 extends well below port 248 so that when valve sleeve |56 moves vbelow the cut-off position shown in Fig. 2, port 248 is always covered. The right-hand end of governor lever |44 is hinged on a pin 266 in projection 225 and its left-hand end is held by spring |45 against the lower end of adjustment screw |41. The position of valve 256, as set by adjustment screw |41, determines the point in the upward travel of valve sleeve |56 at which port 248 commences to be uncovered and flow of air through conduit 55 begins.

The position ofgovernor valve sleeve |56 is in accordance with the balance between the downward force of spring 234 and the upward thrust of speedresponsive vdevice 224. When these two forces are in equilibrium, valve sleeve |56 is stationary and the amount of opening of port 248 and hence the now of air through conduit 55 is determined'by the position of the upper edge of port 248 with respect to the upper edge of valve 256. As long as port 243 is covered by valve 256, there is no now of air through conduit 55 and hence the pressure 'pM in bellows |34 is equal geesten to the compressor absolute discharge pressure 21D,- and. if other factors affecting engine operation are constant, a state of steadyoperation .is maintained. If now the' engine speeds up, owing say to a reduction of the load thereon, speed responsive. device 224 will overcome the force of spring 234 and push up valve sleeve |56 until the increased force of spring 234 again balances the new force of device 224. If the' upward travel of sleeve |56 is suiiicient to 'uncover aA part of port 248, air will commence to flow through conduit 55 and reduce the pressure @5M in bellows |34 below the compressor absolutedischarge pressure pD in conduit' 52 owing to the effect of restriction 53. This reduction in pressure pM in bellows |34 causes a reduction in the variable control oil pressure pc and hence the flow of fuel to the engine, with consequent slowing down oiengine speed, as hereinafter described, until the original speed is restored.

The position of lever |44, as set by adjusting screw |41, determines the amount of opening of port 248 for any given movement of sleeve 56', hence the setting of lever' |44 may be used to limit the maximum opening of port 248 which in' turn determines the maximum flow of air through conduit' 55, the minimum pressure pl.'I in bellows |34', and the minimum variable control oil pressure pc. The adjustment ofV the position vof lever |44, by screw I4?, may therefore be used to establish a minimum value of the variable control oil pressure 20's in order to avoid burner blowout and consequent engine stoppage'.

Coordination of the manualami speed control systems Both cam ||6 in the manuali. control system and cam |50 in the speed control system are fixed to control shaft 60 for simultaneous clockwise operation as controlV lever 64, Fig. l, is advancedv clockwisel through the predetermined range. In the embodiment. shown, the total range of movement of lever 64 is approximately 100.

In a condition of steady stateV operation at constant speed.v and constant fuel flow, the positions of' all movable elements in both the manual. and thesp'eed control systemsv are fixed except' in respect to rotation, main servo` valve |06' and governor valve sleeve |56 are in their neutral positions, pressurel (pe) is substantially constant, and as subsequently explained and as shown in Fig. 2', mairr oatin'g lever H2 is supportedby arm 36S and' rod |14.

When control lever 64 is advanced' clockwise from the position shown in Fig. 1f to another position within the rst 90 range of movement of` the lever, the lift of cam H6' decreases and push'v rod H4 islowered, allowing main floating lever ||2 to turn clockwise, thereby moving main servo valve l below its neutral position. Simultaneously with movement of cam HE, however, cam |50 also turns clockwise to elevate push rod assembly |46 and to thereby turn' setting" lever 43 count'erclockwise on pin 23e. The downward forceof governor spring is thus increased and governor valve sleeve |56 is depressed' from its neutral position in respect to valve 256. Since valve 256 covers port 24S for all positions of sleeve ibelow its neutral position, as shown in Fig. 2, no aircan flow from conduit 55 through recess 256, port 246, annular chamber 26|", port 262g annular groove 263 and conduit i toV the outside atmosphere. Hence, the pressure (pM) in bellows. |34 remainsl unaffected. and continuesv to equal pressure pD. y

The' amount of clockwise movement of lever" ||2 about connection ||3 is limited always by` push rod ||4`. Hence, the manually operated. cam H6 determines the position of the right end ofA lever ||2, since the speed control system is at this time ineffective. The fuel fl'ow to the engine corresponding` to agiven position of the engine control lever is thereby rendered maximum dur'- ln'g acceleration of the engine. The maximum fuel flow during periods of acceleration is determined by the controlL lever setting acting through cam Hit, and not by the diiierence betweenl actual speed and desired speed. This limitation of the fuel ow during acceleration is'4 necessary to prevent overheating of the engine. As long as the increased speed ofthe enginey is below the maximum speed corresponding to' the setting of lever |44 by adjusting screw |41, p'ort- 248 remains covered by valve 256 and the over'- speed mechanism |42 remains ineffective.

However, if the engine speed continues to increase until it approaches the value corresponding to the position of lever |44 and valve 256;

governor valve sleeve l 56 rises to a point where it begins to uncover port 243, whereupon air corn-` mences to now through conduit 55 and reduce they pressure, (pM) in bellows |34 below the pressure (10D). This causes the variable control pressure (10c), and hence fuel flow to the engine, to be decreased as described above, with resulting decrease in engine speed, until said speed is restoredv to the value determined by the setting of lever |44 by adjusting screw 41.

When control lever 64 is retarded in a counter'- clockwise direction from one position to anotherv in the 0-90 range of lever movement, reversal of the above process takes place. Simultaneously with upward movement of rod H4, push ro'd assembly |45 is lowered so that setting of lever |48 reduces the deflection and load of governor spring 2-'34 and governor valve'sleeve |56 is pushed up by the thrust of speed responsive device 224 until the downward forceof the spring 234 again balances the upward thrust of device 224. As long as the upward movement of valve sleeve 256 is insuflicient to uncover any part of port 248, the overspeed mechanism |42 remains ineffective. If, however, the rise oiV sleeve 255 is suicient to uncover a .part of port 248, air will commence to v flow through conduit .'55 and reduce the pressure (pM) in bellows |34 below the pressure (pD). This' causes the variable oil control pressure (pe) and fuel flow to the engine to decrease until the engine speed is reduced to the value determined by the setting of lever |44 by adjusting screw |41.

Concurrent with the lowering of push rod assembly |46 by cam |50, push rod ||4 is raised by cam H6. This causes counterclockwse r0- tation of iloating lever ||2 which lraises main power servo valve m8, with consequent reduction of variable control oil pressure (pc) and engine speed to correspondv with the new lposition of control lever 64.

As control lever 64 is moved between its 90 and quadrant positions, the lift of cam |50 remains substantially constant at a maximum value. The engine speedv therefore has a substantially constant maximum value when the lever is in' its 530%100o range of travel. Within this range, however, the lift ofcam I6 continues to increase to a maximum value corresponding to theext're'me or. 100 positioncf lever 64. Respense' of the combined manual and speed conacteert.`

trol systems to movement of the control lever" in this ten-degree range is similar to that in cases previously explained in which the fuel flow and engine speed vary as a function of both the manual and speed control systems, except that the speed control system is effective to override the manual control system to a relatively greater extent in order to maintain a substantially constant maximum value of speed. As the fuel flow is increased at constant maximum engine speed, the engine torque and hence the brake-horsepower increase, the maximum brake-horsepower being developed at the 100 lever position. The adjusting screw 243 may be set to cause actuation of spring 240, if desired, at any position of cam |50, and to thereby establish the maximum speed at a lower value than is otherwise obtainable as a function of the lift of the cam. Al ternatively, if desired, the lift of cam |50 may be allowed to increase throughout the 100 range of lever movement.

Barometric control system In the barometric control system, the upper end of bellows |34 is fixed inside casing 12 directly over bellows |36 which is oi substantially the same effective area and which has its lower end fixed to a portion of wall |84. A bar 208 rigidly connects the free ends of the bellows to each other so that expansion or contraction of either is accompanied by an equal and opposite movement of the other. A cylindrical stop 289 is provided to limit contraction of bellows |36. Inside bellows |34 and at its upper end there is an adjustable spring support 218 the position of which can be varied as desired by means of a nut 212. Between the lower end of support 210 and the upper end of bar 258 there is a tension spring 214 for biasing the bellows and bar assembly upward in opposition to the differential (pM-p). A cover 21B and a gasket 218 are provided for enclosing support 213 and nut 212 which, upon removal of cover 216, are accessible from the exterior of the casing. The barometric lever |28 is hinged at approximately the mid-position of its length on a pin 333 in bar 268, the left end of the lever being connected to the upper end of barometric valve |24 by means of a pin-and-slot connection 280 which permits vertical movement of valve |24 in sleeve |25 as the angular position of lever changes. The right-hand end of lever |28 has a pin-and-slot connection 28| with a rod 282 fixed to the barometric power piston |25. The upper end of rod 282 above its connection with lever |23 is hinged to a link 204 which is pivotally connected to the left end of positioning bar 283 by means of a pin 288 on which turns a roller 250 engaged with the fixed barometric cam |30. The position of cam |30 is fixed by a pair of pins 232 and 294 respectively fitted into fixed supports 296 and 202. The cam is slidable on the pins so that it can be removed from the apparatus for replacement or any other desired purpose. The right-hand end of positioning bar 233 has a pin 238 xed therein on which the circular bearing 203 is mounted. Roller 200 is held in contact with the upper surface of cam |30 by means of another roller 330 which is rotatable Von a pin 302 fixed in a triangular bracket 12 304. spring 303, compressed between the link and one side of the bracket, holds roller 300 against the lower side of cam |30. Thus, as rod 282 moves in a vertical direction, link 284 follows so that roller 230 remains in engagement with the contoured upper face of cam |30. Both vertical and angular movement are imparted to link 284 in this process so that: when piston |28 and rod 282 descend, bearing 208 is moved leftward and the downward force on main power piston ||0 due to spring 204 is increased; and, similarly, when piston |26 and rod 282 rise, bearing 208 is moved rightward and the downward force on the main power piston H0 is decreased.

The barometric servo valve |24 is undercut to provide a pair of annular chambers 308 and 3|0 between the valve and sleeve |25 in which thev valve is slidable. The vertical position of valve sleeve |25 in reference to casing 12 is fixed and the sleeve is rotated by means of a gear 3|2 driven from shaft |1| through a suitable connection (not shown). pairs of ports 33|, 332, and 333.

In all operating positions of valve |24, ports 33| open into the annular chamber 303 and ports 333 open into the annular chamber 3|0. Fluid in chambers 308 and 3|0 is maintained at pressures designated (10,) and (p4), respectively, as later explained.

Ports 332 are just closed when valve |24 is in its neutral position, as shown in the drawing, the width of the ports being substantially equal to the width of the valve land 334 between the lower end of chamber 308 and the upper end of chamber 3|3. The outlet passage |38 in sleeve |25 is also just closed by the land at the lower end of the valve and outlet passage |40 is similarly just closed by the land at the upper end of the valve, when the latter is in its neutral position.

Ports 332 are connected to the end of conduit |03 so that the ports 332 are continuously supplied with fluid at pressure (p1). Ports 333 are connected to one end of a conduit 322 which has its other end connected to an expansible cham` ber 324 below piston |23. Ports 33| are connected to a pair of conduits 328 and 328. Conduit 328 is connected to a check valve chamber 330 in wall |64 above the barometric power piston I 26, for transmitting the pressure (1),) to chamber 330 from chamber 338. Conduit 326 is supplied with duid from chamber 308 at pressure (pa) and is intermittently connected by means of a slot 340 on main drive shaft 58 to a conduit 338 for sup plying fluid at a pressure (p4) to a chamber 321 above piston |25. Slot 340 intermittently connects conduits 328 and 328 as it rotates and is descriptively referred to as a chopper valve. It serves to restrict flow between conduits 326 and 328. The area of slot 340 is substantially greater than that of an equivalent fixed restriction between the two conduits. A number of parallel slots may be substituted for the single slot 340, if desired.

When the barometric servo valve |24 is elevated above its neutral position, iiuid is permitted to flow from annular chamber 308 through outlet |40 to reservoir 14, thereby reducing the pressure (11,) in conduits 325 and 328. Simultaneously, fluid is permitted to flow from conduit |06 through port 332, chamber 3|0, and conduit 322 to chamber 324, thereby increasing the pressure 1195) in chamber 324i.

When valve |24V is depressed below its neutral position, fluid is permitted to iiow from conduit Bracket 304 is pivoted to'link 284 and, a"

The valve sleeve has three I3? |||6i through 332r and 308;y to. con-.-V duits 326 and 328, thereby irrcreasing.-y the pres-4 sure (pil in conduits'v 326 and 328.` Simultaneously, fluid' fl'owsrfromA chamber 3|.0` through outlet |38 to'reservoirPM'; thereby/reducing thefvalue 5` ingl lever.V |28' cloclrwise on fulcruin pin 33tA and. of pressureI (pg) in; conduit 322 and chamberr32'4. movingl servo valve |24' upwardsl toward its neu- The position of rod 268' and; hence the position traliposition. The downward movementcf. piston f Dl 336'- S determined by the'y IiileSSureA dii'er- |26 and rod 282 continues until the'neutral posiential (45h12,.) actingon bellows- ISK-and |36 and tion of valve |24 is` restored and rod.282 is in. a by'spring 214', there being' a different predeter- 10 new posit-ion corresponding to the neutral posi.- mined positn Of the Din" fel. each Value' 0fY the tion of the'valve and the new lower xed position dinerential, at any given fixed. positionk of spring of pin. 336. When equilibrium occurs, pressures. support 210; In: steady stateoperationwhen the (pp and' (pg) are again substantially constant. barometric servo valve isin its. neutral. position, Inf the above train of events', the particular asshown.- the' positions ci the: power piston |26y 15 value acquired' by the differential (ia-n.)- in reand 0f 10d 232 are predetermined by the pesi* storing` valve l2@ to its'v neutral position is not. tion ot fulcrur pini` 33e and thc'pres'surc dicrimportant; since all that is required. is that the; ential (mailt) acting' '011 listelfl 2-6'. This diff position of rod 232 corresponds to the neutral ferentiallhasasubstantially constant valuewlien.4 position; 0f the Valveif movement of rod 232 the" baremerie Centr-01 S11-Stem iS in equilibrium, 20 is opposed by frictional or other forces, theconand equals' zero when'` the apparatus 00H-V trol; operates to vary the differential'prpp'sufv structed soltliat no force-fisfrequired'- to maintain ci-ently 1;"0 @umpe'nsate'v such. foi-ces'. During. thebear-irre 208'1na11y fixed position correspondine process;v checkt valve :i4-4 reina-ins seated, since. to a xed.' position: of pini 33t;v theY- pressure. (p.) cannot increase above thepresd 'Ihefbarometric control system variesthe posi- 25 sure (ps). tion: of. power. pistonL |26- and roda 2.82 tofmain- When the pressure differential (pn-p0) or tain servo' valve 521|. its neutral'. position as (pM-goo)- decrea'ses', with the barometric control the' lJOSftOlr- 0fv fflerllnl lJ'iI- 335' Changes in 1esystem in an. initial state of.- equilibrium', bar'268 SJ'IlSetGi (5I-'langes irlth'efvalu'e oftheJ differential n X and pin- 336 rise' causing! clockwisev movement of.

www5); Thepressure:` 11M isa function of the compressor discharge pressure pi,- yand is equal thereto, eirceptwhenthe overspeed governor." |152- opens port 248 which` reduces the pressurey pM; toa value. below that of D, but even then pM is still a function. of pn. The pressure pt is zero, so the pressure dii'erential 10D-l., is the absolute compressor discharge pressure; andf therefore the pressurediier'ential' ptip is aifiinction ci" the' absolute compress discharge press-ure' which 321 alcove tne'- power piston'.v Therate of. change' of pressure. (pp is ac function. of chopper valve 340; Asi-the differential increases, thebarometric`A power piston Hetmoves` downward, thereby turn'- leve'r" |23 about its pivotal connection with rod 2821 and" raising the servo' valve |242abo'ut its neu'- tralposition. As. previously explained, pressures (p3) or (15,) decrease andpressureip.) increases, thereby? causing: piston- |26', rod 282, and the ri'ght-hand en'dofilever |281to move upwardly-so that the servo valvemoves downward toward? its neutral'. position. During" this process, decrease'V in the value of.' pressure (pti all'owscheck valve 341i to' move eitvvard,I thereby' allowing' fluid to var-ies directlywitht'he baroi'n'etricx pressure out- 4" ilow from; chamber 32'! sothai',4 pressure (11,) desidel the engine. 'The barometric control` system. creasesfmorea rapidly thanwomd be permitted by therefore position'sibearing 20'21"A as a; function of reversed? ilow from: conduit 333 through chopper the barometricpressure; The powerfoifpositione valvecco; tiene@ fedi ze: moves upwardly (in a ing beair'ie 25B Supplied lyf the hydrauliclsys'- fuelfnow.' decreasingdirection) more rapidly than tem. The downward load' on main" power piston3 it moves downwardly (in a fuel. now increasing lf3 due toL spring Zt is therefore' mofdied dire'ctio'nfi. This" action provides astabilizing eiaccordance with the balolnetric" pressure. fect` on thes'peed governing system. Equilibrium hamber32lfi's connectedtoche'clivalve chain of.- thebarometric controlsyst'em. is restored with berv 33|? by a conduit 31u-'for` flow` from chamber valve. |24' in'. ite'iieutralfp'ostion, withfulcrum pin 32T', past a'balc'heck valve'ldint'oehamber 33E; 50 33$ilin a newhigh'er fixed position; with. 1od2282 when the pressure (22,) exceeds pressure in chamber eetl by a sn'iall am'oifint' predeterm ed byaspring'ttwnich loads-th'evaive. The' che is valve prevents reverse ow from chamber 33`0`i toi conduit 32 at all times.

Considering the barometiio contrer System iii-- dependently of'themanual controly speed controllandother component control systems, whencondition of equilibrium is distinbed' by an i j creasecoinpressor dischargepressu-re (p-5" dr hence when the differential? (p5-12J or (piu-tgl increases, bar 2te and fulcrurn pinl 336 are ered to a new position. The right end of baro-- metric floating" lever' |23- is not affected luntil pressure changes produc'ec by the" v'al've cause' movement op'i'ston |f2`e'. D'ownw'ard movement of` pin 35 causes downward movement of' the servo. Valve |223 and consequent increase' of presesur'e (p3-Y in chamber tilt"andconduits'` 32dand'4 32o.y as previously explained. and-f alsoidecre'ase of pressure (p5) in chamber. 3HE, conduit 322, andi chamber 32d below power piston |26. Incre'f'fts'eV of, pressure` (pg) conduit. 31251- produces afow through chopper' valve-,Belin resulting af coreresponding, increascfinipifessure? 613,1v inichambel: 75

Cal

in. a., corresponding new higher.' position in which the upwalfoliv andi downward forces on the rodare ini` eduilibriuim. with. check. valve 3ds againz seated.. Aslisapparentffrom. the' drawing.; whenr movement of fulcrum pin 326 displaces the' baro- Iri'etric". s'er'vo. valve |24' in' either direction from its'neutral position, tliebarometric power piston |21@ is required to move approximately twice as far in the same direction? to restore the valve tof its neutral position..

Thermal control' system The thermal control system is essentiallyr aV means for overriding the manual control system to reduce the fuel new and.l engine'speed when a predetermined limiting value of temperature is exceeded;

Thermal-'control e, as shown, includes a body Sie ony which.. is xed: a thin walled tube 350 having-1 its right' end closed. Body 3dB is provided with av pair of chambers 352 and 354 separated by an apertured wall 35S and connected to:corlfduits` its Hi8; respectively'. A rod.` 358 isxed-.t'ol-the closed rightend of tubev 35%? and is' slidablyy operable in'. the.` apertured. end. oi"

body 348 on which tube 359 is assembled. The left end of rod 358 is contoured as a valve 35D which is normally seated in wall 355 to prevent low from chamber 3543 to chamber 352. Tube 358 and rod 353 are made from materials having substantially diferent coelicients of thermal expansion, so that when the tube and rod are heated, the tube expands faster than the rod, the thermal control generally being made so that the valve remains closed until the predetermined limiting temperature is exceeded. The control is installed with tube 358 exposed to the engine temperature, as in the tail pipe 33 of the engine of Figure l. Then, when the tail pipe temperature exceeds the limiting value, the valve opens to permit now from conduit |58 through chamber 35e, past valve 338, into chamber 352, and through conduit |52 to reservoir 14. The pressure (p6) in conduit |30 is decreased as valve 368 opens.

The thermal piston |55 functions as a chopper valve similar to chopper valve 348 in the barometric control system. It consists of a generally cylindrical center portion operated in an apertured portion of wall |54 by means of a shaft 332 which is rotated concurrently with shaft |1|. A push rod 354 is attached to the upper end of the piston and extends through wall |55 for engagement, under conditions to be specied,

with a finger 358 ixed to push rod i4. A chamber 358 is provided above piston |55, and the latter is biased upwardly by a spring 318. Piston |55 is provided with a slot 312 so that when the piston is rotated, chamber 358 is intermittently connected through slot 312 to the upper end of conduit |51 leading to main uid conduit |35 and to one end of conduit 314, the other end of which is normally closed by push rod 238.

When valve 358 in thermal control 1l) is closed, the pressure in chamber 358 is maintained at pressure (p1), as in conduit |51, and piston |55 is held down so that push rod 334 does not contact nnger 355. When the limiting engine temperature is exceeded, however, valve 358 opens and iiuid is drained from chamber 358, the pressur@ therein thereby being reduced owing to a drop across slot 312, so spring 315 forces valve |55 up and causes push rod 334i to engage finger 338, causing the latter to rise and move the main floating lever H2 in a -counterclockwise or fuel flow decreasing direction. A decrease of the value of pressure (pc) results and the fuel ilow and engine speed are decreased below the values corresponding to the manual control setting. The flow remains at its decreased rate until the engine temperature is reduced to or slightly below the limiting value, whereupon thermal control valve 35i) closes, valve |55 moves down, and normal operation is resumed.

The thermal control used in the fuel control apparatus need not necessarily be the particular type shown since any temperature responsive device functionally equivalent to control 18 may be employed if desired.

Provision is here made for operating the thermal control system, as follows:

Fluid may be supplied at pressure (p1) to conduit 314 from a conduit 313 which is connected to conduit |83. This supply is controlled by an annular groove 318 in a portion of rod 238 which is guided by a portion 318 of casing 12. The ends of conduits 31e and 314 enter portion 319 of casing 12 and are separated from each other by rod 233 when the position of cam |58 corresponds to any position of the' engine control lever ina preselected range of` movement of lever 64,

which may, for example, be the O90 range. When the control lever isfurther advanced, however, the lift of cam |50 increases so that conduit 314 is opened through groove 318 to conduit 316. At normal engine temperatures, no flow occurs past groove 318 since the same pressure (p1) exists on both sides of it. However, when the limiting engine temperature is exceeded and thermal control valve 358 opens,

chopper valve |55 is supplied with fluid at pres-r sure (p1) by both conduits |51 and 314, and the pressure in chamber 358 corresponding to any opening past valve 350 is greater than in the previously explained case in which conduit 314 was closed by rod 238.

rIhus, while the action of thermal control 10 is always the same in respect to temperature,

and rate of valve opening, the response of thermal piston |55 is less rapid when the control lever is in its last ten degree or other desired range of travel, in which the engine speed setting remains constant and the fuel flow is manually variable to vary the engine power.

The two kinds of thermal override control are sometimes referred to as applying to normal and emergency operation, respectively. Thus, when the lever is advanced in the -l00 range to increase the fuel flow to obtain increased or emergency power, thermal override is desired to occur less rapidly and at a higher value of temperature than in normal operation .in the 0-90 range of control lever travel.

Coordination ofthe manual, speed, and barometric control systems on main power piston I I0 and hence varying the value of the variablecontrol oil pressure (pc) in chamber |98 and conduits |22 and 5S.

As bearing 288 moves leftward, corresponding to downward movement of the barometric power piston |23 produced by an increase of the pressure diierential (pn-po) or (pM-29o), the force transmitted by the bearing from spring 284 and lever |98 to lever |94 and rod |92 is increased so that the value of pressure (pc) corresponding to the position of main control shaft 50 increases. Conversely, as bearing 288 moves rightward, corresponding to decrease of the diiferential (pn-po) or (pM-po), the pressure (pc) decreases.

It is thus seen that the value of the variable control oil pressure (pc) corresponding to any given position of the manual control lever 54 (Fig. 1), depends upon the barometric and speed control systems, the pressure (pe) increasing as the diiierential (py-p0) or (pH-po) increases, as when the engine speed increases, the speed of night increases, or as the altitude of flight decreases.

Since the compressor discharge pressure (10D) increases'as-ithe engine -speed increases (until 'speed governor |42 cuts'in to modify 11D) ,-it -fol- Y to increase of the differential (D-po) occurs.

only as the engine speed.l increasesA andf asthe barometric control system responds to such'xspeed The barometric control. system thus serves to control acceleration and deceleration..

increase.-

of the engine.

As the entering air density increases directly with speed of night and inversely withaltitude of night, the compressor discharge pressure (19D) and the pressure differential (10D-po) correspondingly increase, and .bearing 288:'moves leftwardto increase the pressure (pc) and the fuel lovvv asabove explained. Conversely, as theflight speed decreases' and the altitude increases, ythe differential (pb-po) decreases and bearing 2013 moves rightward to decrease the pressure (pc). The barometric control is sometimes descriptively referred. to' as the altitude control, and cam |30 is customarily contoured with closer regard toV altitude compensation than t-o acceleration control, particularlysince thelatter is accomplished to some extentby chopper valve seti.

The contour of the barometric cam |30 is made to provide al desired position-of bearing'zts for every value of the'V compressor pressure differential. In steady state operation, in which the temperature control-system. is ineffective4v and the control apparatus is in equilibrium, the fuel iiow isdependent upon: (l) themanualand barometric control systems; and (2) the speed control system which overrides these combined systems to reduce the fuel now at excessive engine speeds, as previously explained.

In the invention disclosed in my. parent'application cited, the cutting in of theispeed governor, due to overspeeding of thevr engine, causes the overspeed piston to rise and reset-the mainpower servo valve and piston which in turn reduces thel variable-oil control pressurel and fuel flowftothe engine, witnresultant reduction of engine speed.

In .the invention herein .disclosed the`= cutting; in

of the over-speed governor opens-.a valve which causes a change in the; compressor discharge pressure (pn) in the barometric control system which in turn varies the variableoil controlpressure pc, with resultant change in fuelliowtoV the engine and enginespeed. The droopf yciA the speed governor is the permanent error in engine speed required to make a .full change inavailablek fuel. flow, andv is generally. expressedfas. a

percentage of speed (R. P. M.) at agivenspeedrange of the engine, .between initiation of governorcut-in and full cut-in. It is usually required. that the droop of the speed governor shall not exceed a specified percentage of engine speedV (R. P. M.) at a specified speed range, a specied compressor discharge pressure (p), and'Qi) degree manual control lever position (full-open throttle).

As aresult of yexperience gainediin thecpera'- tion of'..a fuel. .and;sspeed.; control. apparatus'constructed in accordance with the inventiorr:dis-A closed.-I in my paren-t.l application. cited,t Ifhave 18 foundAr tliattliel droop off the speed governor canbe radically reduced; and''the governorfmade substantially isochronous, by causing the gever:- nor, on cut-in, to vary the pressure in the compressor discharge bellows, which will' act tovar'y the control oil pressure-in the saine manner as a variation in the actual? compressor discharge This novely concept, asv embodied in' the construction disclosed in this application;-

pressure.'

not only radically reduces the droop of-v the speed governor, butA also greatly sirnplii-lesl the control apparatus without yloss of performance.

Fig. 4 shows a comparison between the governor droop curves obtained in actual; performance tests` with a fuel and speed control apparatus constructedA in accordance with the invention disclosedV in my parent application cited, and with a fuel and speed control appara'- tus constructed in accordance with the embodiment of my invention disclosed in Fig. 2 of this In these comparative tests, the

application. performance runs were made under identical conditions; with both governors set to cutI in at an enginespeed of 3,500 R. P. M., a compressor dischargeipressure of pounds per square inch,

gauge," and an initial variable control oil pressure'of'approximately 205 pounds per square inch; gauge. Curve A shows the results obtained.'

with the control apparatus according to the. invention disclosed'in my parentapplication'cited; andcurve B shows the results obtained with the control apparatus according to the embodiment of my invention disclosed in Fig.`2 of this application. From these curves it will be noted that at' 3,800 R; P. M'. (VCO pressureof 90 pounds per square inch), the former. showed a droop of 300" R. P. M., while the latter "showed a corresponding droop of 40 R. P. M., or only 13 percent of.

theA former.

The governor according to Fig'. 2 of'this application'r'educes the VCO pressure, after cut-in, as a function of thel pressure in the compressor'discharge bellows |34, and this pressure depends oni the governor lift, i. e., on thespeed of thegovernorshaft 5S.' Theoretically, the pressurep, in the.. bellows' |3`4'does 'not reach itsv miri'iinurii"- value, after cut-in, until the governor sleeve |56" has'lifted atsuiiici'ent distance'(e..g. 0.125) to" fully uncover the port 248. In practice, however,

the bleed'hole in restriction 53-can Vbe made so small thatany further reduction in VCO after the speed of the engine has exceeded the cut-iny speed by say 175 R. P. M. is too small'to be detected. (See curve B of Fig.- 4.)

In the control apparatus used for the tests indicated in curve B- of Fig. 4, the bleed hole in restriction 53 was size #80 (0.000143 square inch).

Itis'thus apparent that arelatively'small Vincrease in engine. speed about the governor set'- ting Will` very rapidlyjreduce the pressure (pM.)

With a lift of governor sleeve- |56y of 0.01 inch, corresponding to an engine speed in-A lll in bellows |34 and the VCO pressure, with corresponding reduction in fuel i'low and engine speed.

Since a minimum governor droop is desirable, the size of the bleed hole in restriction 53 should be made as small as possible. It was found that a #80 size hole was as small as it was practicable to use and therefore the result shown in curve B of Fig. 4 approaches about as close to isochronism as is possible with the type of control apparatus disclosed in Fig. 2 of this application.

Figure 3 In order to still further reduce the droop of the speed governor and to produce a substantially completely isochronous governor, I have devised the modification of my invention illustrated in Fig. 3 of the drawings.

In this modication, the only changes made in the construction and arrangement of elements shown in Fig. 2 are as follows:

(l) Instead of connecting the interior of bellows |34 to the compressor discharge conduit 52, through a restriction 53, and with a branch conduit 55 to bleed off compressed air whenever port 248 in speed control mechanism |42 is uncovered by valve 256; conduit 52 is connected directly to annular chamber 264 in valve sleeve |56 which in turn communicates through port 248' and conduit 55 with the interior of bellows |34, whenever port 248' is uncovered by the downward movement of valve sleeve |56', relative to the middle land 255 of valve 256'.

(2) Whenever port 248 is uncovered by the upward movement of valve sleeve |56', relative to middle land 255 of valve 256', compressed air is discharged from the interior of bellows |34 through conduit 55', annular chamber 26|', port 262 and conduit l to the outside atmosphere.

From the foregoing, it is apparent that whenever valve sleeve |56 is pushed down by the force of spring 234 so that port 24B is uncovered, compressed air will be fed to the interior of bellows |34 from conduit 52 until the pressure in bellows |34 is equal to the compressor discharge pressure (pn) in conduit 52. When valve sleeve |56' is raised by speed governor 224 until land 255 of valve 256 covers port 248', compressed air at pressure (pn) will be trapped in bellows |34 and will remain substantially at pressure (D), (except for such slight variation in pres- 1 sure as may be produced by a movement of rod 268 and pivot 366 which will slightly expand or contract bellows |34), until port 248 is again uncovered by land 255 of valve 256'. It is also apparent that whenever valve sleeve |56 is pushed up by the thrust of speed governor 224 so that port 248 is uncovered by land 255 of valve 256', compressed air will escape from bellows |34 and rapidly reduce the pressure therein to a value less than pressure (12D). I

It is further apparent from Fig. 3 that a slight overspeeding of the engine above the R. P. M. for which governor spring 234 is set will lift valve sleeve opening port Zil, and quickly reduce the pressure in bellows i3d. This will correspondingly reduce the variable control oil pressure (pc) to the full cut-in value. Theoretically, this reduction in variable control oil pressure requires only an infinitesimal change in engine speed, which means that the speed governor is completely isochronous. Actually, however, it is necessamT to provide a slight overlap of land 255 over port 248', in the order of 6.005 inch, to insure a tight seal in the air circuit of bellows v|34 when governor 224 is cut in, and this involves a droop of a few R. P. M. in actual manufacture. Nevertheless, this droop is so small as to render the speed governor substantially isochronous for all. practical purposes.

As the operation of the fuel and speed control apparatus shown in Fig. 3 is identical with that already described for the construction shown in Fig. 2, except as just indicated above, and the y speed governor of Figure 3 is an all-speed governor, whereas that of Figure 2 is an overspeed governor only, no further description of the operation of the modication of Figure 3 is necessary.

While I have shown and described the preferred embodiments of my invention, it is to be understood that I do not limit myself to the precise constructional details disclosed by way of illustration, as these may be changed and modied by those skilled in the art without departing from the spirit of my invention or exceeding the scope of the appended claims.

I claim as my invention:

l. Fuel and speed control apparatus for an internal combustion engine having a pump separate from said apparatus, for delivering fuel to said. engine, and an air compressor, said pump having means for varying said fuel delivery in accordance with a variable control pressure of a liquid supplied to said pump by said apparatus frein a source separate from said fuel supply; comprising: means for modifying a portion of the discharge pressure of said compressor in accordance with the speed of said engine, and means for varying said control pressure in accordance with said modiiied discharge pressure, so that the fuel delivery of said pump is a predetermined function of compressor discharge pressure` and engine speed.

2. Fuel and speed control apparatus for an internal combustion engine having a pump, separate from said. apparatus, for delivering fuel to said engine, and an air compressor, said pump having means for varying said fuel delivery in accordance with a variable control pressure of a liquid supplied to said pump by said apparatus from a source separate from said fuel supply; comprising: means for modifying a portion of the discharge pressure of said compressor in accordance with a predetermined, maximum speed of said engine, and means for varying said control pressure in accordance with said modiiied discharge pressure, so that the fuel delivery of said pump is a predetermined function of compressor discharge pressure and said maximum speed.

3. Fuel and speed control apparatus according to claim l, including manual control means, operatively associated With said discharge pressure modifying means, for selectively varying the point in the speed range of said engine at which said discharge pressure modifying means becomes effective.

4. Fuel and speed control apparatus according to claim 3, wherein said manual control means includes means for selectively varying said control pressure independently of compressor discharge pressure.

5. Fuel and speed control apparatus according to claim 2, including manual control means, operatively associated with said discharge pressure modifying means, for selectively setting the point in the speed range of said engine at which said discharge pressure modifying means becomesv eiective.

6. Fuel and speed control apparatus according accorcia 2i; tozclaimf;5;:1includingfmeans fradiustin'g thersettingfofs'said pointrr.

'7;` Fuel"i andfspee'd Icon-trol fapparatusiaccording to:claim15`,'i inc'lu'dingtradjustable 1 stopffmeans er limiti'ngi thez effective foperating range ci.' said manualiicontrolimeans:

8i" Fuel' andfspeedfcontrolf'apparatusiraccording to claim? '1,1 Wherein saidf cern-pressor vlfdis'charge pressure :nfio'difying means fr includes .a substantiall'y: completely isochronous speedf'governor;

95Fuel andf speed'control `:apparatus according to claim 1,.v whereinsaidmompressor discharge pressure' 'modifying'.means "includes:l a speed fgovernor 'andimeans for' adjustingthefdrcopofsaid governor "sofasnto .makesaidfgovernorasnearly isochronous as :desiredp 10.'l Fuelifand speedfcontrol: apparatus accord ing tofcla'imtil; including means; 'operativelyasseL ciated withi. said-"dischargepressure modify" "g means, for.v varyingfsaid-imodified compressor-:fdischarge'pressurein accordance With'tliebarometric pressure' of the atmosphere 4outside `kvsaid"engine, so 'that the fuelldeli'v'eryi of 'fsaidf'pump A-i af-pr'ed'ee termined` function ofT said 'I compressor discharge pressure ,1 Ysaid barometric 'pressi-1rej and engine speedi 1'l .'l Fuel and speedY l"con-trol f'apparatus f fory an internal"V combustion engine l having 1 af pump "for delivering-fuel? theretof, and an airn compressor; said''pump having- Imca-ns for1V varying' said fuel deliveryrinf accordance-:with a variable `control liquidzpressure supplied' tosaidfpumpfby saidra'pe paratus; comprising: means formodifyingfapor-- ticnfiofrthefdischargepressurefof 1saidconfmressor imaccordancefwithfa-'selected maximum `speed lof said; engine, means voperatively associated with said .discharge-.pressure modifying` means;l fr varying said" modified E'dis'chargepressure in "accordance Vwith the barometric pressure -of thea-t'- mosphere outside'- said-"engine,-A and; meansrf'or varying `rsaid 'control pressure accordance-with said-@modified discharge pressure; so" that'the fuel delivery of said pumpisfa predetermined-function of'compressordischargepressure;said barometric pressureand `said'.i"maxir'num engin-e1: speed.

12'.`luel and speed 'control-lapparatus" accorde ing to claim 11, including manual :controlv means operatively"associatedwith sai-d discharge pressure modifying means, .for selectively `varyingfthe pointin the speed range of said engine at which said discharge-pressuremodifying means becomes eifectivef` 13. Fuelfsand speed control app'aratusffaccordf ingg-.tosclaim l1, including mearrsefor modifying said control pressurejnaccordan'ce Withfengine temperature- -and op.eratively iassociatedl manual controlv means for selectivelysetting the pointin the' ltemperature ,range of...saidia`:engine atiwh-ich saldi4 control: pressuremodifyingemeanslbecomes effective.;

14 Fuel 'and .speedcontrolieapparatus'facccrde ingto `cla-1:11.13, includingmeansfor adj listing-'the setting of said point..

15; Fuel-and speed..control,.apparatusffaccorde ing toY vclain1l2, ,includingadiustable stop-*means for limiting the eifective operating range of said manual control means.

16. Fuel and speed control apparatus according to claim 11, wherein said compressor discharge pressure modifying means includes a speed governor and means for adjusting the droop of said governor so as to make said governor as nearly isochronous as desired.

17. Fuel and speed con-trol apparatus according to claim l, including means operatively asso-` ci'ated-Ll with said i discharge pressure @modifying means;- frmodifyingv a f' portion 'r of said! .come pressor discharge pressurev iniaccordance. .with-the temperatureoffthe exhaust gases insaid engine; sothatl the fuelidelivery of said pump isapredetermined'.v function of compressorV` discharge pressure, said temperaiuire 'andi engine speed.-

lil;v liuellandv speed -control apparatus accordiA ingto` f claim` ll, including means, operatively associated I with!` said .discharge pressure modify-`A ing means, for modifying a portion of said com-i pressor'discharge pressure in accordance withthe temperature/of the exhaust gases in said. engine; so that 4the fuel 'delivery ofisaid pump-is Va pres determined functionV of compressor dischargepressure, saidrbarometri'c pressure, said temperatureqan'dengine speed.

19..Fu'el control apparatus. for aninternal combustion enginehaving associated therewith aI fuel-'lpumpand an air` compressor, said pump having'fmeansxfor varying its delivery to said engine;. comprising: a source of liquid under sul# peratinospheric pressure, conduit means for 'the iiow yoftliquid from 'said source, control meansrin said? conduit means,responsive to the discharge' pressure of said"compressor modified according to* engine speedy. forcontrollinga pressure in a portionof :said conduitmeans,v said delivery-vary# ing means being responsive `to said. controlled pressure,'--adevice responsive `to the engine speed, governorfm'eans actuated vby said device for modifyingaportion ofv said compressor discharge pressure according toi engine'speed,- to operate' saidtcontrol means'in a senseto reduce said` fuel fiowf-.when .a predetermined -valueof said speedy is "exceeded, means-fore varying saidv predetermined `value offsp'eed, 'and adjustable stop'means forLflimitingf-the movement of said lvarying means" to :determine them'aXimum value of said speed;

20,vv Control apparatus'asset forth in claimI 19,' including a'. spring-for opposing vmotion of said speed; responsive device lin response to an'increase. in speed,v acam, means foroperating said cam, afoll'ower operated by saidcam,A means'for varying the defiection of said springya motiontran'smittingconnection between' said followerr andff said" deflection varying means, a stop, for limitingmotion `of said deflection varying means inaspeedincreasing sense to determine the `maximum-lvalue -of- Isaid speed; and means insa-id Sconnectipn for"permittingV relative motion between said'lfollo'wer and said deiiectionV varying means when said loamvl operatesisaid follower so as tov move `said defiectionvarying means against said stop; Wher'ebyrm'ovement ofi'said camoperating meansisnot-aiiected by said stop,

2125 Control' 'apparatus as set including manual means for trol meansmf-:ans responsive saidfengineand' effective when a predetermined, value of said temperature is vexceeded tooverride operating said consaid-controlmeans ina senseto reduce said-fuel.` flow; and means operatedv by said vmanual means.r

fr 'varying'said' predetermined-value.

' 22. Control :apparatus for an internal coinbustion engine having an air compressor; comprising: means, responsive to the discharge pressure of said compressor modiiied according to engine speed, or controlling the supply of fuel to said engine; engine speed responsive means for modifying a portion of said compressor discharge pressure, to operate said fuel controlling means so as to maintain said engine speed at a substantially constant value, means responsive to a temperature in said engine for operating said fuel forth in clairnlQ,`

to atemperature-in:

controlling means to reduce the fuel supply when said temperature exceeds a predetermined value, manually operable adjusting means for controlling said speed responsive means to vary said substantially constant speed value, means associated with said adjusting means and operable after said substantially constant speed is set at a predetermined value to increase the temperature value at which said temperature responsive means become effective to reduce said fuel supply.

23. Control apparatus for an internal combustion engine, comprising: means for controlling the supply of fuel to said engine in response to a variable control liquid pressure, and means for controlling said variable pressure including a barometric control system, an engine speed responsive control system for modifying the action of said barometric control system, and a main control system, each of said systems comprising a valve guide, a valve translatable and rotatable in said guide, a cylinder, a piston translatable and rotatable in said cylinder, and means for subjecting at least one end of said piston to a pressure controlled by its associated valve, a base casting, a mounting casting for connecting said base casting to said engine, a shaft driven by said engine and extending into said mounting casting, said base casting having parallel bores therein for receiving said cylinders and at least one of said valve guides, and gearing means driven by said shaft for continuously rotating all said valves and at least one of said pistons.

24. Control apparatus as set forth in claim 23, including pressure responsive means in said barometric control system for operating the valve therein, speed responsive means in said speed responsive control system for operating the valve therein, manually operable means in said main control system for operating the valve therein, and a bracket mounted on the face of said base casting opposite said mounting casting and supporting said pressure responsive means, said speed responsive means and said manually operable means.

25. Control apparatus for an internal combustion engine having an air compressor and means separate from said apparatus for supplying fuel to said engine, comprising: means for regulating the flow of fuel to said engine, motor means for positioning said fuel flow regulating means, means responsive to engine speed for modifying a portion of the discharge pressure of said compressor, means responsive to said modied discharge pressure for controlling said motor means, and a stop for selectively limiting the travel of said motor means in a fuel ow decreasing direction.

26. Control apparatus as described in claim 25, including means for adjusting the position of said stop.

27. Fuel and speed control apparatus for a turbojet engine having an incorporated air compressor and a fuel pump separate from said apparatus and associated with said engine for delivering fuel to said engine, said pump having means for varying said fuel delivery in accordance with a variable control pressure of a liquid supplied to said pump by said apparatus from a source separate from said fuel supply; comprising: means responsive to engine speed for modifying a portion of the discharge pressure of said compressor, and means for varying said control pressure in accordance with said modified discharge pressure, so that the fuel delivery of said pump is a predetermined function of compressor discharge pressure and engine speed.

28. Fuel and speed control apparatus for a turbojet engine having an incorporated air compressor and a fuel pump separate from said apparatus and associated with said engine for delivering fuel to said engine, said pump having means for varying said fuel delivery in accordance with a variable control pressure of a liquid supplied to said pump by said apparatus from a source separate from said fuel supply; comprising: means responsive to engine speed for modifying a portion of the discharge pressure of said compressor in accordance with a selected maximum speed if said engine, and means for varying said control pressure in accordance with said modied discharge pressure, so that the fuel delivery of said pump is a predetermined function of compressor discharge pressure and said speed.

29. Fuel and speed control apparatus for a turbojet engine having an incorporated air compressor and, means for supplying fuel to said engine, comprising: means for controlling the speed of said engine by regulating the fuel supply thereto, including a droop-type, centrifugal speed governor, driven vby said engine, for regulating the rate of said fuel supply, means, operatively associated with said speed control means, for modifying a portion of the discharge pressure of said compressor according to engine speed, and means, responsive to said modified discharge pressure and operatively associated with said governor for anticipating and accelerating the action of said governor, thereby substantially eliminating its droop, and hence the time lag in the response of said control apparatus to changes in engine speed.

` LEIGHTON LEE II. References Cited in the file ofvthis patent UNITED STATES PATENTS Number Name Date 2,219,994 Jung Oct. 29, 1940 2,341,257 Wnsch Feb. -8, 1944 2,391,291 Bollo et al. Dec. 18, 1945 2,400,415 Hersey May 14, 1946 2,403,371 -Ifleld July 2, 1946 2,410,474 Zeigler Nov. 5, 1946 2,424,035 Ield July 15, 1947 2,450,535 Watson et al. Oct. 5, 1948 2,452,088 Whitehead Oct. 26, 1948 2,528,252 Starkey Oct. 31, 1950 2,560,118 Malone et al July 10, 1951 2,573,724 Neal Nov. 6, 1951 2,576,352 Neal Nov, 27, 1951 

